Infinitely variable injector for improved sncr performance

ABSTRACT

A system for controlling a reagent flow to a furnace in a SCNR process includes at least one injection distribution module (IDM) for supplying water to a plurality of injection lances, metering valves for supplying a NOx reducing agent to the plurality of injection lances, wherein the reagent injection rate of each injection lance is controlled by one metering valve such that a reagent concentration in each injection lance is adjustable and variable from one another. A method for controlling a reagent flow to a furnace includes providing at least one IDM, and for each IDM, providing a plurality of injection lances in communication with the IDM, supplying water to the plurality of injection lances through the IDM and supplying a NOx reducing agent through metering valves, wherein each metering valve controls the reagent injection rate to one injection lance.

FIELD OF THE INVENTION

The present invention relates generally to the reduction of oxides ofnitrogen (NOx) emissions produced by lean burn combustion sources. Inparticular, the present invention provides a system and method for animproved selective non-catalytic reduction (SNCR) process by controllingthe flow of a NOx reducing agent to a furnace during fuel combustion.

BACKGROUND OF THE INVENTION

SNCR has traditionally been applied to industrial and utility boilers,incinerators, and process heaters for the reduction of nitrogen oxideemissions from lean burn combustion sources. In SNCR, a reagent such asaqueous ammonia or aqueous urea is injected into a furnace zone wherethe temperature is typically 1700-2200 F. The reagent decomposes in thehot furnace gas and goes through a number of chemical reactions thatconvert nitrogen oxides into water vapor and nitrogen gas without theuse of a catalyst.

Hundreds of SNCR systems are in commercial service around the world andthe basic SNCR chemistry is well known to those skilled in the art.While it is lower in capital cost than selective catalytic reduction(SCR) of NOx systems, SNCR suffers from lower levels of NOx reductionand poor chemical utilization in part due to temperature variation andunequal NOx spatial distribution across the large dimensions of afurnace. Incomplete chemical reactions lead to secondary pollutants suchas ammonia slip (NH3) and carbon monoxide (CO).

It has been traditional to inject a very dilute solution of the reagentin water, with a reagent concentration in the range of 2-10%, and may beas low as 2% to accommodate the high temperatures and the largedimensions across a furnace. Water provides cooling of individualwater/reagent droplets as well as mass and momentum to the droplets sothat they penetrate across the furnace. In a typical SNCR system, achemical circulation pump circulates an aqueous solution of 32-50% ureafrom a bulk storage tank over to a chemical metering and mixing skidwhere the aqueous based reagent is further diluted with additional waterand pumped to separate injector distribution modules (IDM). At eachdistribution module, the diluted reagent is further split to supply anumber of individual injectors. The chemical flow rate to each injectormay be monitored and adjusted at the injector distribution module, butthe reagent concentration, which comes from the common mixing skid, isfixed and the same to all injectors. The diluted reagent may by atomizedby air along the supply line and/or at the injector. The atomizingairflow to each injector may also be monitored and adjusted at theinjector distribution module using standard valves.

The dilution rate of an aqueous reagent in the chemical mixing skid maybe controlled by using a control valve or a variable speed pump. Whenthe dilution rate changes, the concentration of the reagent solution inthe mixing skid changes, yet the concentration of the reagent solutionflowing from the mixing skid at any time is the same to all distributionmodules and to all injectors. But in reality, the NOx concentration inany one section of the furnace may vary from section to section and fromelevation to elevation, especially as load or fuel or the fouling ofheat transfer surfaces changes in the furnace. The temperature profilein the furnace also shifts with load. Thus, there is a need fordynamically adjusting the amount of NOx reducing agent fed intodifferent positions of a furnace.

The art has continued to seek methods of improving the NOx reductionperformance and chemical (e.g., ammonia, urea) utilization in a SNCRprocess while preventing the production of other pollutants.

U.S. Pat. No. 4,780,289 to Epperly discloses a process for NOx reductionin an effluent from the combustion of a carbonaceous fuel whileminimizing the production of other pollutants. The process comprisesdetermining a NOx reduction versus effluent temperature curve for eachof a plurality of treatment regimens, and introducing (most commonly byinjecting) a NOx treatment agent into the effluent according to a NOxreducing treatment regimen such that the treatment agent is operating onthe high temperature or right side of its NOx reduction versus effluenttemperature curve for an efficient NOx reduction. Epperly teaches thatadjusting dilution/introduction rate and relative presence of enhancersof the treatment agent will shift the curve and thereby cause theintroduction of the treatment agent to operate on the right side of thecurve.

U.S. Pat. No. 4,777,024 to Epperly is directed to a multi-stage processfor reducing the concentration of pollutants in an effluent. Treatmentagents are injected into the effluent of different temperature zones,respectively, to reduce the concentration of nitrogen oxides in theeffluent from the combustion of a carbonaceous fuel. The treatmentagents include urea/ammonia and an enhancer selected from a group ofspecific compounds. But the cost, availability, and storageconsiderations of the enhancer make the already complicated multi-stageprocess very unattractive.

Furthermore, U.S. Pat. No. 4,830,839 to Epperly describes a process forammonia scrubbing by use of a non-nitrogenous treatment agent.

U.S. Pat. No. 5,252,298 to Jones takes a different approach forimproving NOx reduction efficiency. Jones describes an apparatus forinjecting reagents into a combustion effluent through a nozzle, whereinthe nozzle may be aimed in response to the temperature of an effluent.In a preferred embodiment, four injector assemblies are used with equalquantities of injection mixture from each nozzle.

U.S. patent application Ser. No. 10/290,797 to Valentine teaches the useof a metering valve to introduce a total volume of dilution water andreagent to a SNCR lance through an injector tip in a SNCR process.Unfortunately, Valentine fails to recognize the high level of dilutionwater required in a SNCR reagent injection and the physical limitationsof readily available metering valves of the automotive fuel injectortype (i.e., a solenoid actuated metering valve) proposed for use byValentine. In SNCR applications, the reagent concentration in water istypically less than 10% and often is only 2-5%. The injection rate ofcombined dilution water and reagent for each SNCR lance is typically inthe range of 1.0-1.5 gpm (gallons per minute), or 60-90 gallons per hourof mixed liquid per SNCR lance. However, a solenoid actuated meteringvalve has a high-end injection rate of 7-10 gph and perhaps up to 15gph. Thus, the Valentine method falls short of being practical usingcommercially available small capacity valves. The Valentine method wouldrequire the use of, and/or the development of, a much higher capacitytype of metering valve than a solenoid actuated metering valve.

Therefore, there is still a need to provide a system and method forimproving SNCR performance. Desirably, the system and method are able toadjust the injection rate of a NOx reducing agent at each SNCR injectorto better match the reagent injection to the local NOx concentrationacross the furnace, while at the same time maintaining relativelyconstant water and air flow to the injectors to keep the droplet sizeand penetration into the furnace consistent. It would also be desirablefor the injectors placed on the furnace wall to be pivotable withrespect to the wall surface so as to target the reagent injection to apreferred temperature zone inside the furnace.

SUMMARY OF THE INVENTION

It is an objective of the invention to provide a system and method forimproving SNCR performance.

It is a more specific objective of the invention to provide a system andmethod for independently adjusting the injection rate of a NOx reducingagent at each SNCR injector in order to better match the reagentinjection to the local NOx concentration across a furnace during fuelcombustion in a SNCR process.

It is another specific object of the invention to provide a system andmethod which utilize readily available small capacity metering valves todeliver the reducing reagent in a SNCR process.

It is a further specific objective of the invention to provide a systemand method for flexibly adjusting the angular direction of each SNCRinjector placed on a furnace wall to target the reagent injection to apreferred temperature zone in the furnace.

These and other objectives are achieved by providing a system forcontrolling a reagent flow to a furnace which includes at least oneinjection distribution module, wherein each injection distributionmodule is in communication with a plurality of injection lances andsupplies water from a water supply, through the injection distributionmodule, to the plurality of injection lances, wherein each of theplurality of injection lances is in communication with a metering valvemounted on a waterline upstream of the injection lance and downstream ofthe injection distribution module, and wherein the metering valvesupplies a reagent solution and controls the reagent injection rate tothe injection lance such that a reagent concentration in each of theplurality of injection lances is adjustable and variable from oneanother.

In some embodiments, the system further comprises a mixing sectionarranged in a water line downstream of each injection distributionmodule and upstream of each injection lance for mixing water with thereagent solution supplied by the metering valve to create a dilutedreagent solution. The diluted reagent solution is then supplied to theinjection lance. In preferred embodiments, the system further comprisesa source of atomizing air in communication with the injection lance forsupplying pressured air to the injection lance to create an atomized,diluted regent solution. The injection lance which has influxes of twosources of fluid/air (i.e., a diluted reagent solution and air) iscalled twin-fluid injection lances.

In certain embodiments, the injection lance is a three-fluid injectionlances wherein the reagent solution, water, and air all flow to a mixingchamber inside the injection lance to create an atomized, diluted regentsolution.

Moreover, the invention provides another system for controlling areagent flow to a furnace which includes a mixing skid for mixing areagent solution supplied by a master metering valve and water to createa diluted reagent solution, at least one injection distribution modulein communication with the mixing skid for receiving the diluted reagentsolution, a plurality of injection lances in communication with the atleast one injection distribution module for receiving the dilutedreagent solution, wherein each of the plurality of injection lances isin communication of an individual reagent metering valve for controllingan injection rate of the diluted reagent into the injection lance.

In some advantageous embodiments, the adjustment of the reagentinjection rate by the metering valve is automatically controlled by aprogrammable logic controller (PLC).

In some advantageous embodiments, the plurality of injection lances ofthe system are positioned on a wall of the furnace through holes oropenings for injecting the diluted reagent to the combustion zone of thefurnace, wherein each injection lance is pivotable with respect to thefurnace wall about at least one axis, so that an angle at which theliquid is injected into the furnace is infinitely variable.

Furthermore, the present invention provides a method for controlling areagent flow to a furnace in a SNCR process comprising the steps ofproviding at least one injection distribution module, and for eachinjection distribution module, providing a plurality of injection lancesin communication with the injection distribution module, supplying waterand a reagent solution to the plurality of injection lances via theinjection distribution module and metering valves respectively, whereineach metering valve controls the injection rate of the reagent solutionto one injection lance.

In some embodiments, the injection lances are twin-fluid lances, whereinthe method further includes mixing water and the reagent solution in amixing port to create a diluted reagent solution, delivering the dilutedreagent solution the injection lance, and supplying pressured air to theinjection lance from a source of atomizing air to create an atomized,diluted reagent solution.

In some embodiments, the injection lances are three-fluid lances,wherein the method further includes mixing water, the reagent solution,and pressured air in a mixing chamber inside an injection lance to forman atomized, diluted reagent solution.

The present invention further provides a method for controlling areagent flow to a furnace in a SNCR process which comprises the stepsof: mixing a reagent solution with water in a mixing section to create adiluted reagent solution, supplying the diluted reagent solution to aninjection distribution module in communication with the mixing section,distributing the diluted reagent solution to a plurality of injectionlances in communication with the injection distribution module, andcontrolling an injection rate of the diluted reagent solution to each ofthe plurality of injection lances via an individual metering valve.

In some embodiments, the method further includes the step of injectingthe diluted reagent solution to a chamber of the furnace through theinjection lances mounted on a furnace wall through holes or openings,wherein each injection lance is pivotable with respect to the furnacewall about at least one axis, so that an angle at which the dilutedreagent solution is injected into the furnace is variable. In preferredembodiments, the angle of each injection lance is automaticallycontrolled by a PLC based on information acquired by sensors.

Other objects of the invention and its particular features andadvantages will become more apparent from consideration of the followingdrawings and accompanying detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of part of an injection system for reducingan amount of pollutants produced during combustion of fuel in accordanceto one embodiment of the invention, wherein the lances are twin-fluidinjection lances.

FIG. 2 is a schematic view of part of an injection system for reducingan amount of pollutants produced during combustion of fuel in accordanceto another embodiment of the invention, wherein the lances arethree-fluid injection lances.

FIG. 3 is a schematic view of part of an injection system for reducingan amount of pollutants produced during combustion of fuel in accordanceto a third embodiment of the invention, wherein a stock of pre-dilutedreagent solution is prepared and used.

FIG. 4 is a schematic, cross-sectional view of pivotable injectionlances placed on a furnace wall in according to one embodiment of thepresent invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention utilizes a metering valve in communication witheach injection lance for controlling the delivery of a NOx reducingreagent (e.g., aqueous ammonia, aqueous urea solution) to each injectionlance. Compared to the prior art method which mixes the reagent anddilution water at a chemical mixing skid and delivers the dilutedreagent solution to an injection distribution module, the currentinvention advantageously requires that only dilution water be deliveredto the injection distribution module(s) and the reagent is then added tothe dilution water at a point just upstream of each individual SNCRinjector. In this way, the reagent injection rate to each SNCR injectionlance may be individually controlled by the metering valve andconsequently, the reagent concentration in each of the injection lancesis adjustable and variable from one another. It should be understoodthat the terms “injector” and “injection lance” are usedinterchangeably.

The reagent metering valve may be mounted on a dilution water line inclose proximity to each injection lance feeding each injector. Thereagent injection rate for each reagent metering valve may be controlledby a PLC or laptop computer by varying the pulse width of the injectionvalve. Moreover, the reagent feed rate to each SNCR lance injecting intoa furnace may be established in advance by a computational fluiddynamics (CFO) modeling. It is known that the CFO modeling is useful toidentify zones of high NOx concentration and/or temperature variationsacross the furnace by predicting these parameters, by field mapping ofthe NOx concentration in the furnace at different injection rates may beperformed using furnace probes, by monitoring the furnace load ortemperature, or by monitoring the downstream outlet NOx or ammoniaconcentration in the exhaust duct as a function of different reagentinjection rates from the SNCR injectors.

An injector of the type identified in U.S. Pat. No. 7,467,749 may beused as a metering valve and may be easily adapted to the currentinvention by inserting a connection in the dilution water line from theinjector distribution module over to an individual SNCR injection lanceto accept the metering valve. Alternatively, in other embodiments, theSNCR injection lance may be modified to make it a three-fluid lance byfitting a pulse width modulated metering valve to the end of theinjection lance. In such cases the SNCR injection lance will generallyhave an atomization chamber at the distal end where the dilution water,reagent, and air are mixed for atomization before traveling down thelength of the lance for injection into the furnace through a tip. Insome cases a three-fluid lance may be easily modified to a traditionaltwo-fluid SNCR lance by switching the air and liquid (dilution water)connection points on the lance so that the reagent from the meteringvalve is mixed with the dilution water in a first chamber of the lanceand then the mixed liquid is atomized by the introduction of atomizingair. In other cases, a modified three-fluid injection lance may bedesirable.

FIG. 1 illustrates one exemplary embodiment of the present inventionwhich utilizes twin-fluid lances. Water is pumped from a water supplyskid (10) to at least one injection distribution module (20) whereindividual water lines are branched off from each of the IDMs which areeventually connected to individual injection lances (30). On each waterline, a metering valve (50) is connected to downstream of thedistribution module (20) and upstream of the injection lances (30) forintroducing an aqueous urea solution of typically 32%-50% concentrationinto a port (60) connected to the dilution water line downstream of thedistribution module (20) and upstream of the injection lance (30) formixing the urea solution with water. The resulting diluted urea solutionis pumped into the injection lances (30). On each injection lance, asingle or multiple atomizing air connections (70) are mounted to allowsupply of pressurized air to atomize the dilute solution in theinjection lance (30). The atomized diluted urea solution then travelsdown the injection lance (30) for introduction into combustion gases. Insome embodiments, the port (60) may reside in a first chamber of theinjection lance (30) and the diluted solution flows from the firstchamber to the rest of the injection lance (30) for mixing withpressured air to form an atomized, diluted reagent solution.

In some embodiment, the metering valve (50) may be of the return flowtype with urea supply to the valve and return to storage or arecirculation line, or it may be of the non return flow design. Thereturn flow injector, as described in U.S. Pat. No. 7,467,749, thespecification of which is incorporated herein in its entirety, isparticularly suitable for use as the metering valve (50) in thisapplication.

In some embodiments, all the metering valves (50) may be positionedremotely from and fluidly connected to the injector and/or injectionlance. Each of the metering valves may be manually or automaticallytuned.

In some embodiments, the metering valves comprise a pulse widthmodulated solenoid valve. In additional embodiments, the metering valvescomprises a variable speed chemical feed pump.

The use of multiple and individually controlled twin-fluid lances systemallows for a higher degree of flexibility. By varying the on time of themetering valve (50), the concentration of urea solution introduced intothe furnace through each lance (30) may be varied. As such, the totalamount of the reagent injected though a particular injection lance overa period of time can also be easily controlled. Other types oftwin-fluid lances which are known to one skilled in the art of SNCR canalso be used in the prevent invention.

In some embodiments, the concentration of urea solution in eachinjection lance may be controlled by a programmable logic controller orany other suitable controller as a function of: combustor load, fuelflow rate, exhaust gas flow rate, temperature, NOx concentration beforeor after the SNCR process, ammonia slip, carbon monoxide concentration,or any combination of those sensor measurements. The concentration ofurea solution may be adjusted to provide a necessary quantity of urea toan individual injection lance, or section of lances, to achieve desiredemissions. This allows for precise tuning of the reagent injectionthrough the injection lance or section of lances while maintaining theother NOx reduction conditions.

FIG. 2 illustrates another embodiment of the invention which involvesthree-fluid (water, urea solution, and air) injection lances (30). Wateris pumped from a water supply skid (10) to a single or multipleinjection distribution modules (20) where individual water lines arebranched off from each of the IDMs (20) which are connected toindividual injection lances (30). On each injection lance (30), ametering valve (50) fed from a supply of urea solution is connected tointroduce an aqueous urea solution (40) of typically 32%-50%concentration into a mixing chamber (80) reside inside the individualinjection lance (30). The mixing chamber (80) is also connected with thewater line for receiving water from the injection distribution module(20). Compressed air is introduced into the chamber (80) by a single ormultiple atomizing air connections (70) for atomization. The atomizeddiluted urea solution then travels down the injection lance (30) forintroduction into the combustion gases via a tip.

The current invention, as illustrated in FIGS. 1 and 2, only requiresthat the metering valves introduce a much smaller and more concentratedvolume of reagent to each individual SNCR injection lance than that ofthe prior art. As such, small capacity metering valves which are readilyavailable in commerce can be used in the current invention. For example,on a 139 MMBtu incinerator requiring NOx reduction using SNCR, the totalquantity of a 32% solution of aqueous urea reagent required is 13gallons per hour. The SNCR design requires three SNCR injection lancesfor adequate distribution of mixed reagent across the furnace injectionzone. The total dilution water flow rate using standard SNCR designfactors is 180 gallons per hour. Therefore, in the prior art approach(see U.S. patent application Ser. No. 10/290,797 to Valentine), each ofthe three SNCR injection lances would need to be supplied by a meteringvalve having the ability to flow and meter one-third of the totalcombined flow of 193 gph, or roughly 64 gph/lance. In contrast, thecurrent invention has each of the three SNCR lances individuallysupplied with 60 gallons per hour of water from a pressurized dilutionwater line; and into each individual water line is inserted a meteringvalve injecting one-third of the total 13 gph of 32% urea reagentrequired by the process, or 4.3 gph. The flow rate of 4.3 gph of ureareagent is easily accommodated by commercially available solenoidactuated metering valves or injectors as recognized by the currentinvention.

In FIG. 3, a master metering valve (55) is mounted to a dilution watersupply line and connected to a urea supply (40). The 32%-50% ureasolution is pumped by the master metering valve (55) into a port (65)upstream of an injection distribution module (20) for mixing with waterto yield a diluted urea solution. The diluted urea solution flows to theinjector distribution module (20) and then split off through separatelines on the distribution module (20) and placed in fluid contact withinjection lances (30). Three individual reagent metering valves (50) incommunication with the three injection lances (30) respectively may beused to control the diluted reagent solution flowing into the respectiveinjection lances (30).

The embodiment in FIG. 3 is suitable for small furnaces which requireonly a few injectors or a single level of injection. In this situation,the reagent concentration to the multiple SNCR injectors fed from theIDM will be the same, but the reagent concentration in the master mixingskid may be easily and nearly instantly controlled by changing the pulsewidth signal to the metering valve at the water inlet to the IDM.Locating the master metering valve on the inlet water line at thedistribution panel will reduce the cost of the metering equipment andalso reduce the time lag versus traditional systems where the reagentconcentration is adjusted at a mixed chemical skid located remotely fromthe injector location. For reagent flow rates beyond the capacity of thesingle master metering valve, multiple metering valves may be installedon the water inlet to the IDM. If desired, metering valves may beinstalled at convenient locations on each dilution water outlet linefrom the IDM for individually control each of the injection lances.Though the reagent concentration to each injection lance is the same,the reagent amount injected to each injection lance, which is determinedby the time and frequency of injections, may be individually andinstantly controlled or adjusted from a PLC based controller by varyingthe pulse width of the injection valve (percent on time).

The metering valves that are suitable for use in the embodiment of FIG.1 can also be used in the embodiments of FIGS. 2 and 3.

In yet another embodiment, the SNCR injection lances of FIGS. 1-3 may bemounted on retractable and tilting mechanisms as described in U.S.Application Publication No. 2006/0008393, which allows for the injectorspray to be pointed upwards or downwards as temperature in the furnaceshifts with load, fuel or furnace slugging conditions. This approachhelps to better match the injector spray to the targeted temperaturezone in the furnace. Using the tilting mechanism with the individualreagent control at each injector allows a near infinite number ofinjection strategies.

FIG. 4 shows a schematic, cross-sectional view of a furnace withpivotable injection lances placed on the furnace wall. In FIG. 4, afurnace (110) contains at least one, but typically many, burner (112),located in a combustion chamber (114) defined by a wall (116). It shouldbe understood that the term “furnace” is used herein for the sake ofsimplicity, but that the term is intended to encompass boilers, furnacesor any other like device in which is combusted a fuel. In the normaloperation of the furnace (110), combustion air and fuel are supplied tothe burner (112), and the fuel is burned as shown at a position (118) inthe lower portion of combustion chamber (114). Since operation offurnaces of the type disclosed herein are extremely well-known, theseaspects of the system are not discussed in detail herein.

The injection lances (30) are placed around the periphery of the furnaceperimeter at multiple levels to better match the injection location tothe optimum temperature window. Typically each level of injectors has adedicated injection distribution module. Passing through the wall (116)of the furnace (110) is at least one opening or hole (120) through eachof which passes an injection lance (30) through which a NOx reducingagent is injected into the furnace (110). Each injection lance (30) ispivotable with respect to the furnace wall (116) about at least one axis(as indicated by double-ended arrow B) such that the angle at which thepollution reduction substance is injected into the furnace (110) isvariable. In some preferred embodiments, the axis about which theinjection lance is pivotable is generally horizontal and that the angleof injection lance is in a range of +/−20 degrees from horizontal. Theplurality of injection lances (30) may be used to inject the reagentsolution of same concentration, but in most circumstances, they are usedto inject the reagent of different concentration.

The injection angle and reagent injection rate at each injection lancemay be controlled manually from a laptop computer or automatically froma PLC controller. As described before, the PLC controller works in apreprogrammed manner by using an exit NOx, ammonia signal (i.e., ammoniaslip), a furnace load signal, a furnace temperature sensor, or otherfurnace operating characteristics like the timing of soot blowers orother signal representative of the relative slagging condition of thefurnace. Accordingly, the system may further comprise one or moresensors for providing the sensed conditions regarding NOx emission,ammonia slip, furnace load and feed rate, and/or furnace gastemperature.

Although the invention has been described in connection with variousillustrated embodiments, numerous modifications and adaptations may bemade thereto without departing from the spirit and scope of theinvention as set forth in the claims.

1-13. (canceled)
 14. A system for controlling a reagent flow to a furnace during fuel combustion in a selective non-catalytic reduction (SNCR) process, said system comprising: a port arranged in a water line and in communication with a water supply; at least one master metering valve in communication with said port for supplying a reagent solution and controlling a reagent injection rate to said port, wherein the reagent solution and water are mixed in said port to create a diluted reagent solution; at least one injection distribution module in communication with said port for receiving the diluted reagent solution; and a plurality of injection lances in communication with said at least one injection distribution module that supplies the diluted reagent solution to said plurality of injection lances, wherein each of said plurality of injection lances is in communication of an individual reagent metering valve positioned upstream of each of said injection lances and downstream of said port, and wherein said individual reagent metering valve controls an injection rate of the diluted reagent solution into each of said injection lances.
 15. The system of claim 14, wherein each of said plurality of injection lances passes through a hole in a wall of the furnace, wherein each of said injection lances is adapted to inject liquid therein to a chamber of the furnace, and wherein each of said injection lances is pivotable with respect to the wall of the furnace about at least one axis, so that an angle at which the liquid is injected by each of said injection lances into the furnace is variable. 16-22. (canceled)
 23. A method for controlling a reagent flow to a furnace during fuel combustion in a selective non-catalytic reduction (SNCR) process, the method comprising: supplying a reagent solution to a port through at least one master metering valve, and controlling a reagent injection rate to the port, wherein the reagent solution and water are mixed in the port to create a diluted reagent solution; supplying the diluted reagent solution to at least one injection distribution module in communication with the port; and supplying the diluted reagent solution to a plurality of injection lances in communication with said at least one injection distribution module, wherein each of said injection lances is in communication with an individual reagent metering valve positioned upstream of said each of the injection lances and downstream of the port, and wherein said individual reagent metering valve controls an injection rate of the diluted reagent solution into said each of said injection lances.
 24. The system of claim 14, wherein a reagent amount in the diluted reagent solution supplied to each of said injection lances is separately adjustable by the individual reagent metering valve in the communication of said each of the injection lances.
 25. The system of claim 14, wherein a reagent concentration in the diluted reagent solution is adjusted by said at least one master metering valve.
 26. The system of claim 14, wherein reagent concentrations in the diluted reagent solution supplied to said injection lances are the same.
 27. The system of claim 26, wherein a reagent amount in the diluted reagent solution supplied to each of said injection lances is separately adjustable by the individual reagent metering valve in the communication of said each of the injection lances.
 28. The system of claim 14 further comprising a controller in communication with the individual reagent metering valve for adjusting a pulse width of the individual reagent metering valve to control the injection rate.
 29. The system of claim 14, wherein the individual reagent metering valve includes a pulse width modulated solenoid valve.
 30. The system of claim 14, wherein said at least one master metering valve includes a pulse width modulated solenoid valve.
 31. The system of claim 14 further comprising another master metering valve in communication with the port for supplying the reagent solution to the port.
 32. The method of claim 23, wherein a reagent amount in the diluted reagent solution supplied to each of the injection lances is separately adjustable by the individual reagent metering valve in the communication of each of said injection lances.
 33. The method of claim 23 further comprising adjusting a reagent concentration in the diluted reagent solution via said at least one master metering valve.
 34. The method of claim 23, wherein reagent concentrations in the diluted reagent solution supplied to said injection lances are the same.
 35. The method of claim 34, wherein a reagent amount in the diluted reagent solution supplied to each of said injection lances is separately adjustable by the individual reagent metering valve in the communication of said each of said injection lances.
 36. The method of claim 23 further comprising adjusting a pulse width of the individual reagent metering valve to control the injection rate.
 37. The method of claim 23 further comprising supplying the reagent solution to the port through another master metering valve;
 38. The method of claim 23, wherein each of said injection lances passes through a hole in a wall of the furnace, wherein each of said injection lances is adapted to inject liquid therein to a chamber of the furnace, and wherein said each of the injection lances is pivotable with respect to the wall of the furnace about at least one axis, so that an angle at which the liquid is injected by each of said injection lances into the furnace is variable. 